An optocoupler is placed in series between the field ground pin of digital input circuitry and the field ground of an industrial controller. A capacitor to field ground is provided for each digital input. A resistor is provided to the input pin of the digital input circuitry. To detect a broken wire a test pulse is provided to the optocoupler connected in the ground path. This test pulse isolates the digital input circuitry from field ground. As current is always being provided from the field when the wire is not broken, the capacitor connected between the input and ground charges. After the test pulse has completed, the output signal of the digital input circuitry is examined. If the level indicates the input is high, the wire is not broken. If, however, the output remains low indicating that the input is low, the wire has broken.

The present invention introduces an arrangement for enhancing the performance of an electronic circuit comprising a phototransistor (Q). Either a common-collector or a common-emitter connected phototransistor (Q) has a main resistor (R.sub.L), and at least one external bias resistors (R.sub.L2, R.sub.L3, R.sub.L4), each in parallel to one another. The microcontroller may directly control the voltage outputs or act via respective switches (S1, S2) regarding each respective resistor. When the electronic circuit with the phototransistor (Q) is switched on, at least one of the external bias resistors (R.sub.L2, R.sub.L3, R.sub.L4) are switched on. The voltage output rise time is short, and when the bias has been set, the external bias resistor(s) are disconnected functionally. This means that during the actual measurement with the electric circuit, only the main resistor (R.sub.L) is used in the connection.

The invention provides a universal semiconductor switch. The universal semiconductor switch includes a switching arrangement having an input and an output, at least one trigger circuit operably coupled to the switching arrangement and a noise immunity circuit coupled to the trigger circuit.

An optical-controlled driving circuit adapts to a high utility power environment with high voltages, large currents and severe surges, and includes an optical-controlled switch circuit, an SCR with optical-controlled driver and a main circuit. The optical-controlled switch circuit includes an optical-controlled component and a first switching transistor that are connected in serial. The SCR with optical-controlled driver includes at least two switching transistors that are connected in serial and a plurality of diodes, and is coupled to the main circuit. The optical-controlled driving circuit generates a driving current according to the voltage of a utility power. When the optical-controlled driving circuit is used in a DC converter using an SCR as a switch element, the optical-controlled driving circuit helps to increase the operation efficiency when the DC converter works under a light load.

In one embodiment, a parasitic capacitance compensation circuit for a switch is disclosed that includes a first inductor operably coupled between a first terminal and a second terminal, and a second inductor operably coupled between the first and second terminals and parallel to the first inductor. The second inductor is switched in when a peak voltage on the first and second terminals falls below a first voltage. The first inductance tunes out substantially all of a parasitic capacitance of the switch when the switch is OFF and the peak voltage is above the first voltage. The first and second inductances collectively tune out substantially all of the parasitic capacitance of the switch when the switch is OFF and the peak voltage is below the first voltage.

An optical-controlled driving circuit adapts to a high utility power environment with high voltages, large currents and severe surges, and includes an optical-controlled switch circuit, an SCR with optical-controlled driver and a main circuit. The optical-controlled switch circuit includes an optical-controlled component and a first switching transistor that are connected in serial. The SCR with optical-controlled driver includes at least two switching transistors that are connected in serial and a plurality of diodes, and is coupled to the main circuit. The optical-controlled driving circuit generates a driving current according to the voltage of a utility power. When the optical-controlled driving circuit is used in a DC converter using an SCR as a switch element, the optical-controlled driving circuit helps to increase the operation efficiency when the DC converter works under a light load.

In one embodiment, an RF power amplifier includes a first transistor and a second transistor in parallel, wherein a gate of the first transistor and a gate of the second transistor are configured to be driven by an RF source. A third transistor comprising a drain is operably coupled to both a source of the first transistor and a source of the second transistor. A control circuit is operably coupled to a gate of the third transistor and configured to alter a gate-to-source voltage of the third transistor, thereby altering a drain current of each of the first transistor and the second transistor, thereby altering an output power of the RF power amplifier.

An isolation system and isolation device are disclosed. An illustrative isolation device is disclosed to include first circuitry having at least a first emitter and a first detector, second circuitry having at least a dual-purpose component, an isolation material configured to electrically isolate the first circuitry from the second circuitry, and switching circuitry adapted to connect the dual-purpose component to emit a first signal for detection by the first detector in a first configuration, and to receive a second signal from the first emitter in a second configuration.

In one embodiment, an impedance matching network is disclosed that includes a first circuit comprising a first variable component providing a first variable capacitance or inductance, and a second circuit comprising a second variable component providing a second variable capacitance or inductance. Each of the first circuit and the second circuit includes plurality of switching circuits configured to provide the first variable capacitance or inductance and the second variable capacitance or inductance. Each of the plurality of switching circuits includes a diode and a driver circuit configured to switch the diode. The driver circuit includes a first switch, a second switch coupled in series with the first switch, and a filter circuit that is coupled at a first end between the first switch and the second switch, and is operably coupled at a second end to the diode.

A digital input circuit adopts a first state when an input signal is below a lower threshold value and adopts a second state when the input signal is above an upper threshold value. The digital input circuit comprises first and second subcircuits that exhibit a non-ideal current output behavior at least in the second state, and each comprises a current stabilizing element with a driving circuit and a voltage stabilizing element. The first and second subcircuits are configured such that, at least in a portion of the second state, an electric current flowing through the first subcircuit's voltage stabilizing element consists substantially of a stabilized current of the second subcircuit, and an electric current that flows through the second subcircuit's voltage stabilizing element consists substantially of a stabilized current of the first subcircuit, such that the non-ideal current output behavior of the first and second subcircuits compensate for each other.